1. Field of the Invention
The present invention relates to an image forming apparatus, such as a printer, a copying machine, or a facsimile machine. More particularly, the invention relates to an image forming apparatus which occupies a reduced area in a place where it is installed for use.
2. Description of the Prior Art
In the general image forming apparatus, a sheet on which an image is to be formed is transported in a horizontal state. Accordingly, the image forming apparatus occupies a large area in the place where it is installed.
The image forming apparatus designed for the purpose of reducing the area occupied by the apparatus is disclosed in Japanese Patent Publication Nos. Hei. 6-202390 and 6-202395.
FIG. 7 is a perspective view showing the layout of components parts within an image forming apparatus disclosed in Japanese Patent Publication No. Hei. 6-202390. FIG. 8 is a top view of the image forming apparatus of FIG. 7.
As seen from these figures, a sheet container 1, a paper feeding roller 2, a sheet transporting path 3, an image forming unit 4, a fixing unit 5, an exit roller pair 6, and the like are disposed substantially erectly within a case of the apparatus. A sheet S is transported while standing substantially upright.
With such a construction, the image forming apparatus may be vertically set when it is installed. As a result, the apparatus installing area is reduced.
FIG. 9 is a perspective view showing the layout of components parts within an image forming apparatus disclosed in Japanese Patent publication No. Hei. 6-202395. FIG. 10 is a perspective view showing a discharging state of printed sheets S.
As seen from these figures, a paper cassette 1', a paper feeding roller 2', a photoreceptor drum 4', a fixing roller pair 5', and the like stand substantially erect, so that a sheet S is transported while standing substantially upright.
An exit roller pair 6' is mounted slantwise. With the slant, the discharged sheets S are brought down in the slanting direction and laid upon another successively, as shown in FIG. 10.
In the publication (Japanese Patent publication No. Hei. 6-202395), the exit roller pair 6' stands substantially erect, and a tray 7 for receiving discharged sheets S is provided, as shown in FIG. 11.
In the apparatus disclosed in published Unexamined Japanese Patent Application No. Hei. 6-202390, the sheet S is transported while standing substantially erect. The sheets, which are put in the sheet container 1, stand substantially upright. In the container, a part of each sheet is pressed by the paper feeding roller 2, while the remaining part of the sheet is free. Accordingly, the remaining part thereof is tiltable to the right or the left, viz., unstable. The sheet being transported along the sheet transporting path 3 is unstable, viz., swingable to the right and the left.
The sheet has a toner image transferred thereto by the image forming unit 4. If the sheet vibrates during the course of the movement of the sheet up to the fixing unit 5, toner of the toner image is shaken from the sheet (the toner image will get out of shape). Therefore, the resultant image will be poor in quality.
In the conventional apparatus, between the image forming unit 4 and the fixing unit 5, the sheet is transported in a state that only the end of the sheet is held between a sheet transporting belt 8, which comes in contact with the toner transferred surface of the sheet, and a guide plate 9. In such a construction, the sheet transporting belt 8 and its drive system are indispensably provided. The result is a complexity of the sheet transporting means.
Although not described in the publication, the sheet transporting belt 8 for holding the end part of the toner transferred surface of the sheet is allowed to be provided for only the lower end part of the sheet. Accordingly, the upper end part of the sheet still vibratory, and there is the possibility that the toner image will be lost in its shape. An additional sheet transporting belt 8 may be provided for the upper part of the sheet. However, this structure cannot support the sheet of different size. To cope with this, the upper sheet transporting belt may be mounted vertically movably. However, this approach makes the related structure more complicated.
The same thing is true for the apparatus described in Japanese Patent Publication No. Hei. 6-202395.
In either conventional apparatus, the sheet S is transported in a state that it stands upright. The behavior of the sheet S is unstable, and hence its handling is difficult.
The handling of the sheets discharged by the exit roller pair 6 is not described in Japanese Patent Publication No. Hei. 6-202395.
In the apparatus of the publication, the sheets are discharged to be scattered on the apparatus installing place. In those scattered sheets, some sheets are faced up and some sheets are faced down.
A solution to the scattering problem is disclosed in Japanese Patent Publication No. Hei. 6-202395.
In a first solution, as shown in FIG. 10, an exit roller pair 6' is mounted slantwise. The discharged sheets S are successively laid upon another successively on the installing place. In a second solution, as shown in FIG. 11, the exit roller pair 6' stands erect, not slanted, and a tray 7 receives discharged sheets S.
In the first solution shown in FIG. 10, the printed surfaces of the discharged sheets S are all turned upward (faced up), but the edges of the sheets are not trued up. Further, the discharged sheets are laid upon another on the installing place. A large area in the installing place is occupied when the apparatus is used. This is adverse to the object to reduce the area occupied by the apparatus.
In the second solution shown in FIG. 11, the printed surfaces of the discharged sheets are all faced up, and the edges of the sheets are trued up.
The discharged sheet tray 7 is slanted to the outside of the apparatus (turned counterclockwise in FIG. 11), and provided on the front side of the apparatus case. Accordingly, the area occupied by the apparatus is increased, and this fact is also adverse to the object to reduce the occupied area.